Today's market for amphiphilic molecules, including surfactants, emulsifiers, wetting control agents, drug and gene delivery agents, microencapsulents, nanoparticle growth agents, cleaning products, and food and cosmetic additives, is mostly comprised of synthetic surfactants prepared from petroleum-based starting materials. Not only have many synthetic amphiphiles shown acute toxicities in water supplies and soil after being deposited, but they also are dependent on nonrenewable and increasingly costly petroleum. The solution to this ongoing problem is the synthesis (biological and/or chemical) of naturally-occurring (e.g. biosurfactants) or new, biodegradable amphiphilic glycolipids. Although many amphiphilic glycolipids are used in industry, they are difficult to produce on a large scale and purity is often low. A low-cost synthesis of glycolipid amphiphiles is a requirement in a market that includes many oils and synthetic amphiphiles that can be produced at pennies per pound.
As one example of biosurfactants, rhamnolipids consist of one or more rhamnose (i.e., 6-deoxy-α-L-mannose) moieties and an ester-linked di-lipid tail. They have been found in the Gram-negative bacteria such as Acinetobacter calcoaceticus, Enterobacter asburiae, Enterobacter hormaechei, Pantoea stewartii, and Pseudomonas aeruginosa. Biosynthetic production of rhamnolipids via the mutant strain of bacteria, P. aeruginosa ATCC 9027 (a mutant that produces specifically monorhamnolipids) produces about 40 different monorhamnolipid congeners with a variety of saturated and unsaturated lipid chain lengths (ranging from C6 to C18); the fully-saturated C10,C10 monorhamnolipid being the most dominant (˜80% of mixture). Rhamnolipids, and many known amphiphilic glycolipids, are good foaming and wetting agents and are able to increase aqueous solubility of hydrophobic compounds, making them excellent solubilizing and emulsifying agents for diverse applications. In food, rhamnolipids are used as emulsifiers (e.g., partial broken fat tissue) and for influencing the rheological properties of flour. In agriculture, they are used for dilution and dispersion of fertilizers and pesticides in order to increase product penetration into plants. In cosmetics, they are used as soaps and soap formulators. In industry, they are used for emulsion polymerization of paints and industrial coatings. In the pharmaceutical industry, they are used to influence hydrophobicity of Gram-negative cell walls, allowing for easier attack by hydrophobic antibiotics. Furthermore, rhamnolipids have been shown to be environmentally friendly, expressing low toxicity and biodegradable characteristics, as well as showing strong evidence for bioremediation of hydrocarbons, organic pollutants (including green-house gases), and heavy-metal contamination.
Many amphiphiles are naturally-occurring materials that are biosynthesized and extracted from animals, plants and bacteria. However, these compounds are difficult to biosynthesize on a large scale, and purification can be difficult to impossible if a complex mixture of congeners is produced. Based on their putative biodegradability and low toxicity, biosurfactants and other amphiphilic glycolipids have great potential as “green” alternatives to the sometimes carcinogenic and toxic synthetic amphiphiles in the market. More specifically, large-scale production of the glycolipid class of biosurfactants is of great interest because of their excellent surfactant characteristics, their demonstrated use in bioremediation; the existence of evidence supporting their susceptibility to biodegradation, and their applications from paper, plastics, cosmetics, foods, pesticides, medicine, etc.
While there is a high demand for these carbohydrate or a derivative-based surfactants, conventional methods for producing such surfactants require utilizing bacteria or other microorganisms, which significantly increases their production and purification costs. In addition, microorganism based biosurfactant production limits the number of biosurfactants that can be produced and, therefore, surfactant's properties cannot be readily tailored. Many chemical processes for producing biosurfactants often utilize a toxic material or are low yielding, thereby rendering many such processes not commercially viable.
Therefore, there is a need for a cost-effective and environmentally friendly method for producing biosurfactants such as carbohydrate- or its derivative-based surfactants.